A bubble-free vacuum molding forming production method of a high-transparency silica gel key

Abstract

The application discloses a bubble-free vacuum mould pressing forming method of high-transmittance silica gel keys, and belongs to the field of silicone rubber forming process. In the process of filling high-transmittance silica gel material into a mould cavity, high-precision air pressure sensors arranged at multiple positions in the cavity collect pressure data in real time and transmit the data to a controller. The controller performs filtering and differential operation on the pressure data, calculates the rate of change of pressure with time, and compares the rate with a preset threshold to identify whether residual bubbles exist in the cavity. When it is identified that residual bubbles exist, the controller automatically adjusts the rotation speed of a vacuum pump set, the opening degree of an exhaust valve set, and the start-stop of a filling driving device or the filling rate according to a preset control strategy table. When the pressure data meet preset stable conditions and the pressure value falls below an exhaust completion threshold, the controller stops exhaust and filling, performs pressure maintaining and curing, and cools and demoulds. The application realizes online real-time monitoring and hierarchical adaptive closed-loop control of the air pressure in the cavity, and improves the thoroughness of bubble removal and the consistency of products.

Description

Technical Field

[0001] This application belongs to the field of silicone rubber molding process, specifically relating to a bubble-free vacuum molding production method for high-transparency silicone buttons. Background Technology

[0002] Precision products such as high-transparency silicone buttons are usually manufactured using vacuum molding technology. The basic process is as follows: the rubber material is filled into the mold cavity, and the material is cured by heating and pressurizing in a vacuum environment. The core of this process is to remove the gas in the rubber material by vacuuming to obtain a bubble-free and highly dense molded product.

[0003] However, existing technology has a key drawback in compression molding: it cannot obtain real-time air pressure data within the mold cavity. Operators can only pre-set vacuum parameters and holding time based on experience, and the entire venting process is in an open-loop control state, leading to two direct technical problems: It is impossible to determine whether air bubbles have been completely removed. When the viscosity of the adhesive is high or the filling speed is inappropriate, microbubbles and entrained air are easy to remain, which seriously affects the optical transmittance and appearance quality of the product. It is also impossible to adaptively adjust the vacuum parameters according to the actual degassing effect. Due to differences in environment or materials, the same preset parameters cannot guarantee a consistent degassing effect when different batches are produced, resulting in large fluctuations in product yield and poor consistency.

[0004] Therefore, how to provide a molding method that can monitor the gas state inside the cavity in real time and adaptively adjust the venting process to achieve complete elimination of air bubbles and improve product consistency is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] The purpose of this invention is to provide a bubble-free vacuum molding production method for high-transmittance silicone buttons, which can effectively solve the problems in the background art.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A bubble-free vacuum molding method for high-transparency silicone buttons includes the following steps: During the process of filling the mold cavity with high-transmittance silicone material, high-precision air pressure sensors arranged in multiple different positions in the mold cavity are used to collect pressure data of each monitoring point in real time at a preset sampling frequency, and the pressure data is transmitted to the controller. The controller performs filtering and differentiation on the received pressure data, calculates the rate of change of pressure over time, compares the rate of change of pressure over time with a preset threshold, and identifies whether there are residual air bubbles in the mold cavity based on the comparison result. When residual bubbles are identified based on the rate of change of pressure over time, the controller automatically adjusts the rotation speed of the vacuum pump group connected to the mold cavity and / or the opening of the exhaust valve group according to a preset control strategy table, and selectively controls the start / stop of the filling drive device or the filling rate. When the pressure data meets the preset stability conditions and the pressure value drops below the venting completion threshold, venting and filling are stopped, pressure holding and curing are performed, and the finished product is removed after cooling.

[0007] Preferably, there are at least four high-precision air pressure sensors, which are respectively arranged at the gate inlet of the mold cavity, the top center area of ​​the mold cavity, and the two opposite corners of the mold cavity away from the gate.

[0008] Preferably, before the controller performs filtering and differentiation operations on the received pressure data, it further includes: The controller establishes an independent time-series pressure dataset for each monitoring point, and performs filtering, differentiation, and feature extraction on the pressure data of each monitoring point independently. The controller comprehensively determines the overall venting state of the mold cavity based on the comparison results of the pressure change rate over time at all monitoring points with a preset threshold. The venting process is determined to be complete only when the pressure data at all monitoring points meet the preset stability conditions.

[0009] Preferably, the controller compares the rate of change of pressure over time with a preset threshold to identify residual bubbles in the following manner: When the absolute value of the rate of change of pressure over time is detected to decrease by more than a preset percentage threshold within a preset time, it is determined to be a slope change mode, indicating the presence of locally aggregated bubbles. When the detected pressure change is lower than the preset pressure change threshold and the duration exceeds the preset plateau period time, it is determined to be a pressure plateau period mode, indicating the presence of closed island-type bubbles.

[0010] Preferably, the corresponding adjustment strategy is executed based on the different bubble types identified: When a locally aggregated bubble is identified, the controller sends a pause command to the filling drive device to pause the filling for a first preset time and starts a secondary vacuum replenishment procedure, so that the vacuum pump group continues to work for a second preset time during the filling pause. When a closed, isolated bubble is identified, the controller first executes the pause filling and secondary vacuum replenishment procedure. If the pressure plateau is not relieved within a preset judgment time after the secondary vacuum replenishment is completed, a rapid opening and closing command is further issued to the exhaust valve group to quickly close the exhaust valve and then reopen it to the original opening degree within a preset very short time, creating an instantaneous pressure disturbance.

[0011] Preferably, the controller also synchronously analyzes the pressure gradient between each monitoring point: The pressure difference between the pressure measured by a high-precision air pressure sensor at the gate inlet of the mold cavity and the pressure measured by high-precision air pressure sensors at two opposite corners of the mold cavity away from the gate is calculated. When the pressure difference exceeds a preset gradient threshold, it is determined that bubbles have accumulated in a local area of ​​the mold cavity; when the pressure difference is less than the preset gradient threshold, it is determined that the bubbles are diffusely and uniformly distributed. The controller assists in selecting the corresponding adjustment strategy based on the determination result of the pressure difference.

[0012] Preferably, the method further includes a mold preheating step before the filling step: The controller divides the mold preheating process into a rapid heating stage, a heat preservation and stabilization stage, and a stable holding stage; in the rapid heating stage, heating is performed at a preset maximum power. When the mold temperature approaches the target temperature, it enters the heat preservation and stabilization stage, where the heating power is reduced by a PID control algorithm to suppress temperature overshoot; when the mold temperature reaches the target temperature, it enters the stabilization and holding stage, where the temperature fluctuation is controlled within a preset range by dynamically fine-tuning the heating power.

[0013] Preferably, the preset stability condition is: Within a preset time window, the controller performs sliding window analysis on the pressure data of each monitoring point. The pressure curves of each monitoring point tend to be stable and the rate of change of pressure over time tends to be zero. At the same time, the pressure in the mold cavity drops below the exhaust completion threshold.

[0014] Preferably, the method further includes a material preparation step before the filling step: A refractive index matching light-transmitting filler is added to the high-transmittance silicone material, and the refractive index of the refractive index matching light-transmitting filler is controlled to deviate from the refractive index of the silicone matrix within a preset matching range.

[0015] Preferably, after the pressure holding and curing is completed, a cooling and demolding step is also included: Turn off the heating and start the cooling system to lower the mold temperature to the preset safe demolding temperature. Then open the mold and remove the molded high-transparency silicone button from the mold cavity.

[0016] In summary, this application includes at least one of the following beneficial technical effects: 1. This invention utilizes multiple high-precision pressure sensors located at different positions within the mold cavity to collect pressure data from each monitoring point in real time at a preset sampling frequency during the filling process. This data is then transmitted to the controller, enabling digital and visual online monitoring of the internal pressure state of the mold cavity during the molding process. Based on this, the controller performs filtering and differential operations on the pressure data, calculates the rate of change of pressure over time, and compares it with a preset threshold to automatically identify the state of residual bubbles. Subsequently, it adaptively adjusts the speed of the vacuum pump group, the opening degree of the exhaust valve group, and the start / stop or filling rate of the filling drive device according to a preset control strategy table. This overcomes the shortcomings of existing technologies that rely on empirical preset parameters and cannot adjust in real time according to the actual exhaust state, ensuring that the exhaust process is always within the optimal working range. 2. This invention can identify the presence of locally aggregated or closed island-type bubbles in the cavity online based on the abrupt change (slope change mode) or plateau period (pressure plateau period mode) of the rate of change of pressure over time. It can also automatically perform graded adaptive adjustment operations such as pausing filling, secondary vacuuming, and rapid valve opening and closing to create instantaneous pressure disturbances. This ensures that the microbubbles and entrained air in the high-viscosity, high-transparency silicone material are fully removed, effectively avoiding the problem of bubble residue caused by insufficient venting. This improves the light transmission uniformity and appearance quality of the high-transparency silicone buttons, and significantly increases the product yield. 3. This invention monitors the pressure data inside the mold cavity in real time and dynamically adjusts the exhaust parameters, so that the production of each batch is adaptively optimized according to the current actual mold cavity state, thereby eliminating the impact of environmental and material batch differences on the exhaust effect. The multi-point collaborative monitoring mechanism further avoids misjudgment caused by single-point sensor failure or local anomaly, ensuring that the products of each batch have stable and consistent internal quality and optical performance. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the overall process flow of the bubble-free vacuum molding production method for high-transparency silicone key buttons of the present invention; Figure 2 This is a schematic diagram of the core principle framework of adaptive exhaust control in this invention; Figure 3 This is a schematic diagram of the logical flow framework of the silicone material filling and online air pressure monitoring stages in this invention; Figure 4 This is a schematic diagram of the multi-level interaction relationship and data flow between the controller and the vacuum pump, exhaust valve, filling drive device and mold cavity in this invention. Detailed Implementation

[0018] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the following detailed description of specific embodiments based on the present invention is provided in conjunction with the accompanying drawings and preferred embodiments.

[0019] The core of the bubble-free vacuum molding production method for high-transparency silicone buttons proposed in this invention lies in online air pressure monitoring and adaptive exhaust control. By arranging a high-precision air pressure sensor array within the mold cavity, air pressure data from various regions is collected in real time during the filling process. The controller sequentially performs digital filtering, differential calculation, and feature extraction on the air pressure data to calculate the pressure drop rate dP / dt. Then, dP / dt is compared with a preset threshold. Based on the comparison result, it determines whether residual bubbles exist in the cavity and automatically adjusts the vacuum pump speed, exhaust valve opening, filling start / stop, and filling rate, forming a closed-loop adaptive control for the entire vacuum molding process, ensuring that bubbles in the high-viscosity, high-transparency silicone material are fully eliminated.

[0020] The vacuum molding system that implements the above method consists of a mold assembly, a high-precision air pressure sensor array, a data acquisition module, a controller, a vacuum pump group, an exhaust valve group, a filling drive device, and a heating and temperature control device. The structure, connection relationship and working mode of each component are described below.

[0021] The mold assembly includes an upper mold and a lower mold. The upper mold and the lower mold are guided by locating pins and guide pillars to achieve mold closing. The locating pins are fixed to the parting surface of the lower mold, and the guide pillars are installed in the corresponding guide holes of the upper mold. When the mold is closed, the locating pins first contact the guide pillars and guide the upper mold to move along the axis of the guide pillars, ensuring the relative positional accuracy of the mold closing process.

[0022] The lower mold is machined with a mold cavity and a gate. The contour dimensions of the mold cavity are consistent with the design contour of the high-transparency silicone button product to be molded. The surface roughness of the mold cavity is controlled below Ra0.4μm to ensure the appearance quality of the button product. The gate, as the entrance channel for the high-transparency silicone material to enter the mold cavity, is opened in a concealed position on the non-visible surface of the mold cavity side wall. The cross-sectional shape and size of the gate are determined according to the product structure and filling balance requirements, so that the high-transparency silicone material can fill the mold cavity with a uniform flow front.

[0023] The high-precision air pressure sensor array consists of no fewer than four high-precision air pressure sensors, which are arranged at different positions in the mold cavity. One high-precision air pressure sensor is located at the mold cavity inlet near the gate to monitor the air pressure status of the area where the high-transmittance silicone material first enters. One high-precision air pressure sensor is located in the center area at the top of the mold cavity to reflect the air pressure changes in the main area inside the mold cavity. The other two high-precision air pressure sensors are located at two opposite corners of the mold cavity away from the gate to sense the air pressure distribution at the edges and dead corners of the mold cavity.

[0024] Each high-precision pressure sensor is connected to the mold cavity through a pressure measuring hole on the mold body. The pressure measuring hole has a diameter of 2mm and a smooth inner wall. The pressure-sensing end face of the high-precision pressure sensor is fixed to the inner wall of the pressure measuring hole by a threaded seal. A fluororubber O-ring is installed at the threaded connection to ensure the airtightness of the pressure measuring channel under negative pressure. All high-precision pressure sensors are connected to the data acquisition module through a twisted-pair shielded signal line. The shielding layer of the signal line is grounded at a single point on one end of the data acquisition module to suppress electromagnetic interference. The above multi-point coordinated arrangement can cover the mold cavity entrance, center, edge and dead corner areas, enabling the controller to obtain air pressure distribution information at different locations in the mold cavity and avoid monitoring blind spots.

[0025] The data acquisition module performs analog-to-digital conversion on the analog pressure signals output by each high-precision barometric pressure sensor. The data acquisition module has a built-in 16-bit resolution analog-to-digital converter with a sampling rate set to 50Hz, which means that each channel is sampled once every 20ms. The converted digital pressure data is transmitted to the controller in real time through a high-speed communication interface. The high-speed communication interface adopts SPI bus or RS-485 bus with a communication rate of not less than 1Mbps, which meets the real-time requirements of multi-channel synchronous transmission.

[0026] The controller is the core control unit of the entire system. It adopts an ARM Cortex-M series microcontroller with a main frequency of no less than 200MHz or a digital signal processor with equivalent performance. It has built-in FLASH memory and RAM memory. FLASH is used to store control programs, residual gas identification algorithms, adaptive control algorithms and control strategy tables, while RAM is used to cache real-time pressure data and intermediate calculation results.

[0027] The controller is internally equipped with a signal processing module, which includes a digital filter unit, a differential operation unit, and a feature extraction unit. The digital filter unit performs digital filtering and noise reduction on the raw pressure data, filtering out electromagnetic interference generated by high-voltage switchgear and frequency converters, as well as measurement noise caused by mold vibration. The differential operation unit performs differential operations on the filtered pressure data to calculate the pressure drop rate dP / dt. The feature extraction unit extracts features such as inflection points and plateau periods of the pressure curve from the pressure data.

[0028] The controller receives pressure data collected in real time from each high-precision air pressure sensor through the data acquisition module, compares the calculated dP / dt with the preset threshold, and generates corresponding control commands based on the comparison results using an adaptive control algorithm. The control commands are then sent to the vacuum pump group, exhaust valve group, filling drive device, and heating temperature control device.

[0029] like Figure 4As shown, the data flow and control command interaction between the controller and the high-precision pressure sensor array, vacuum pump group, exhaust valve group, filling drive device and heating temperature control device constitute a closed-loop control circuit.

[0030] The vacuum pump unit is connected to the exhaust port of the mold cavity through a vacuum pipeline. The vacuum pipeline uses a pressure-resistant flexible hose with an inner diameter of not less than 10mm, and the connection is reliably sealed. The vacuum pump unit adopts a variable frequency speed control method. The vacuum pump motor is driven by a frequency converter. After receiving the speed control command from the controller, the frequency converter changes the output frequency, thereby adjusting the speed of the vacuum pump motor. The adjustment range of the pumping rate is 20% to 30% of the current level, thereby adjusting the vacuum level in the mold cavity.

[0031] The exhaust valve assembly is also connected to the exhaust port of the mold cavity through a pipeline, forming a parallel exhaust channel structure with the vacuum pump assembly. That is, the air inlet of the exhaust valve assembly and the air inlet of the vacuum pump assembly are connected in parallel through a T-fitting pipe to the exhaust port pipeline, and the exhaust ports are combined and then open to the atmosphere. The exhaust valve assembly uses a proportional solenoid valve, and the driving current of the proportional solenoid valve is linearly proportional to the valve opening. After receiving the opening adjustment command sent by the controller, the exhaust valve assembly changes the driving current, thereby adjusting the valve opening and the effective cross-sectional area of ​​the exhaust port. The adjustment range of reducing the cross-sectional area of ​​the exhaust port is 10% to 20%. By appropriately reducing the cross-sectional area, in conjunction with the pumping action of the vacuum pump assembly, the vacuum level in the mold cavity can be improved.

[0032] The filling drive unit uses an electric injection pump, and the injection screw is driven by a servo motor. The screw diameter and pitch are designed according to the single injection volume. The filling drive unit is connected to the gate through a feeding pipeline, which is a smooth-walled, high-pressure resistant metal hose. The filling drive unit is responsible for injecting the pre-mixed high-transparency silicone material into the mold cavity through the gate. It receives filling and pause commands from the controller and controls the start, stop, and speed of the servo motor to adjust the filling rate. The filling pressure is set in the range of 5MPa to 15MPa. The controller maintains the filling pressure within the preset range by adjusting the output torque of the servo motor.

[0033] The heating and temperature control device includes a heating plate embedded inside the mold and a mold temperature sensor. The heating plate is a resistance electric heating plate, which is embedded in the back processing groove of the upper and lower molds. The power density of the heating plate is determined according to the mold size and heating rate requirements. The mold temperature sensor is a K-type thermocouple with a response time of less than 1s and a temperature measurement accuracy of ±1℃. The mold temperature sensor is installed in a temperature measuring hole 5mm to 10mm away from the surface of the mold cavity.

[0034] The heating and temperature control device is connected to the controller to form a closed-loop temperature control circuit. The controller sends a target temperature command to the heating and temperature control device. After the heating plate is powered on, it transfers heat to the mold body by heat conduction. The mold temperature sensor collects the actual temperature of the mold in real time and feeds it back to the controller. The controller dynamically adjusts the heating power according to the deviation between the target temperature and the feedback temperature using a PID control algorithm to control the mold temperature within ±2℃ of the target temperature.

[0035] like Figure 1 As shown, the bubble-free vacuum molding method for high-transmittance silicone buttons in this embodiment includes the following steps: Step S1: Precisely close and lock the upper and lower molds to form a sealed mold cavity. Then, heat the mold to the preset vulcanization temperature and maintain stability through closed-loop temperature control. Specifically, this includes the following steps: Step S101: The upper mold and the lower mold are closed by a positioning mechanism. The positioning mechanism consists of a guide post, a positioning pin, and a locking device. The guide post and the positioning pin constrain the movement trajectory of the upper mold during the mold closing process. The fitting accuracy of the positioning pin and the guide hole ensures that the relative position accuracy between the upper mold and the lower mold is controlled within 0.02mm, which directly corresponds to the dimensional tolerance of the high-transparency silicone button product. After the mold is closed, the contour accuracy of the button cavity is locked within an acceptable range.

[0036] In step S102, after the mold is closed, the locking device applies a preset mold closing force to the upper and lower molds. The value of the mold closing force is determined based on the projected area of ​​the mold cavity and the filling pressure of the high-transparency silicone material. The filling pressure ranges from 5MPa to 15MPa. The projected area of ​​the mold cavity is calculated from the size of the button product. The value of the mold closing force must ensure that the contact stress of the parting surface is always higher than the peak pressure inside the mold cavity to prevent the parting surface from being stretched open during vacuuming and filling.

[0037] Under the action of the clamping force, the parting surface and mating surfaces of the upper and lower molds fit tightly together, forming a sealed state that can resist the negative pressure environment, providing a structural basis for the initial vacuum establishment in step S2, and preventing outside air from seeping into the mold cavity through the parting surface during vacuuming.

[0038] In step S103, after the mold is closed and sealed, the controller sends a target temperature command to the heating and temperature control device. The typical value of the target temperature is 180℃, which falls within the preset temperature range of 170℃ to 190℃. The resistance heating plate in the heating and temperature control device is energized, and heat is transferred to the mold body by thermal conduction, and the internal temperature of the mold gradually rises. The mold temperature sensor embedded in the mold collects the actual temperature of the mold near the surface of the mold cavity in real time and feeds back the actual temperature data of the mold to the controller.

[0039] In step S104, the controller receives the actual temperature of the mold from the mold temperature sensor and compares it with the target temperature of 180°C. Based on the temperature deviation, the controller uses a PID control algorithm to calculate the heating power adjustment. The proportional coefficient, integral time, and derivative time of the PID controller are pre-tuned according to the heat capacity and thermal inertia of the mold. The tuning goal is to ensure that the temperature response neither overshoots nor exhibits steady-state deviation. The controller outputs the adjustment to the execution unit of the heating and temperature control device, which changes the heating rate by adjusting the input power of the resistance heating plate, thus forming a closed-loop temperature control circuit.

[0040] The mold temperature sensor uses a type K or type N thermocouple with a response time of less than 1 second and a temperature measurement accuracy of ±1℃, which meets the response and accuracy requirements of real-time temperature control.

[0041] Step S105: The mold preheating process is automatically divided into three stages according to the temperature range.

[0042] The first stage is the rapid heating stage. When the mold temperature is below 170°C, the resistance heating plate continues to heat at the preset maximum power, and the mold temperature approaches the target temperature at a relatively fast rate. The core objective of the first stage is to shorten the preheating time.

[0043] The second stage is the heat preservation and stabilization stage. When the mold temperature rises to around 170℃, which is about 10℃ away from the target temperature, the controller automatically reduces the heating power, and the PID control algorithm begins to finely adjust and actively suppress temperature overshoot, so that the mold temperature transitions from rapid rise to a stable temperature approaching 180℃.

[0044] The third stage is the stabilization stage. After the mold temperature reaches 180℃, the controller continuously monitors the temperature fluctuation and controls the temperature fluctuation within ±2℃ by dynamically adjusting the heating power, ensuring that the entire mold body enters a thermal equilibrium state and the temperature of the mold cavity wall tends to be uniform.

[0045] In step S106, after the mold temperature is stabilized within the target temperature range of ±2℃, the controller determines that the preheating process is complete and sends a signal to allow filling. At this time, the mold has the temperature conditions to accept the filling of high-transparency silicone material, and the process can proceed to step S2.

[0046] Step S2: The controller starts the vacuum pump group to pre-evacuate the sealed mold cavity, remove the free air in the mold cavity before the silicone material is filled, reduce the pressure in the mold cavity to the preset vacuum level and maintain standby.

[0047] In step S201, the controller sends a start command to the frequency converter of the vacuum pump group. After receiving the command, the frequency converter drives the vacuum pump motor to run at a preset speed. The vacuum pump starts to pump air from the pipeline connected to the exhaust port and the mold cavity. At the same time, the controller sends a full-open command to the exhaust valve group. The proportional solenoid valve of the exhaust valve group switches to the full-open position, and the flow cross-sectional area of ​​the exhaust channel reaches the maximum to reduce exhaust resistance.

[0048] Step S202: The pre-vacuuming process lasts for a preset extraction time, which is set to 5 seconds. During the extraction process, the controller synchronously receives pressure data collected by the high-precision air pressure sensor located near the exhaust port in the high-precision air pressure sensor array, and monitors the change in pressure value inside the mold cavity in real time.

[0049] When the controller detects that the pressure value drops below the preset pressure threshold, it determines that the free air discharge in the mold cavity has met the requirements. The preset pressure threshold is set to 10 kPa. The value of the preset pressure threshold is determined based on the minimum vacuum required for the high-transparency silicone material to escape bubbles under negative pressure, while also taking into account the pumping capacity and production efficiency of the vacuum pump group.

[0050] In step S203, after the pressure inside the mold cavity drops below 10 kPa, the controller determines that the initial vacuum environment has been established.

[0051] The controller sends a standby command to the frequency converter of the vacuum pump group. The frequency converter reduces the speed of the vacuum pump motor to the preset standby speed. The vacuum pump group enters a low-power maintenance state to continuously maintain the vacuum level in the mold cavity. At the same time, the exhaust valve group maintains its current opening. At this point, the mold cavity has the vacuum conditions to accept the filling of high-transparency silicone material, and the process can proceed to step S3.

[0052] Step S3: The filling drive device is activated to inject high-transmittance silicone material into the mold cavity. Simultaneously, a high-precision air pressure sensor array collects pressure data at various monitoring points in the mold cavity in real time at a frequency of 50Hz. The controller receives and stores the pressure data. Figure 3 As shown, the logical flow of the filling and online air pressure monitoring stages is as follows: In step S301, the controller sends a start command to the filling drive device. After receiving the command, the filling drive device injects the pre-mixed high-transmittance silicone material into the mold cavity through the gate. The viscosity range of the high-transmittance silicone material is 3000 to 8000 Pa·s, and the specific value is determined according to the light transmittance requirements of the product and the filler ratio.

[0053] In a typical implementation, the viscosity of the high-transmittance silicone material is 5000 Pa·s. A refractive index matching light-transmitting filler has been pre-added to the material. The refractive index of the refractive index matching light-transmitting filler is selected to match the refractive index of the silicone matrix. The typical matching deviation is controlled within ±0.02. As a result, the refractive index difference between the silicone material and the residual air is reduced, and the scattering and reflection loss of light at the bubble interface is reduced, thereby improving the light transmission uniformity of the molded product.

[0054] In step S302, the filling drive device injects high-transparency silicone material into the mold cavity in a constant pressure mode or a constant rate mode within a preset filling pressure range of 5 to 15 MPa. In the constant pressure mode, the controller maintains the filling pressure at a preset value by adjusting the output torque of the servo motor. In the constant rate mode, the controller maintains the advance speed of the injection screw at a preset value by adjusting the rotation speed of the servo motor.

[0055] After the high-transparency silicone material enters the mold cavity through the gate, it expands gradually from the inlet area to the far end along the mold cavity contour under the filling pressure until it fills the internal space of the mold cavity. During the filling process, the flow front of the high-transparency silicone material carries some residual air to form microbubbles. The partial vacuum environment established in step S2 provides the driving force for the initial escape of the bubbles.

[0056] The above-mentioned filling and material configuration enables the high-transmittance silicone material to be stably filled into the mold under controllable pressure, and the introduction of refractive index matching filler reduces the impact of air bubbles on optical performance at the material level.

[0057] In step S303, at the same time as the filling drive device is started, all the high-precision air pressure sensors in the high-precision air pressure sensor array start working synchronously. Each high-precision air pressure sensor collects the air pressure data of the corresponding monitoring point in the mold cavity in real time at a sampling frequency of 50Hz. The high-precision air pressure sensor adopts a piezoresistive high-precision sensor with a pressure measurement accuracy of ±0.1kPa and a response time of less than 20ms.

[0058] In one specific implementation, the high-precision air pressure sensor array includes four piezoresistive high-precision air pressure sensors, which are respectively arranged at the mold cavity inlet near the gate, at the center of the top of the mold cavity, and at two opposite corners of the mold cavity. Each high-precision air pressure sensor is connected to the data acquisition module through a twisted-pair shielded signal line to suppress electromagnetic interference.

[0059] In step S304, the data acquisition module receives the analog pressure signals output by each high-precision barometric pressure sensor, performs analog-to-digital conversion on the analog pressure signals with 16-bit conversion accuracy and a 50Hz sampling rate, and transmits the converted digital pressure data to the controller in real time through a high-speed communication interface.

[0060] After receiving digital pressure data, the controller establishes an independent time-series pressure dataset for each monitoring point. The pressure data of each monitoring point is synchronously stored in the controller's data buffer. The data buffer has a capacity of at least 5 seconds of continuous sampling data for use in the subsequent sliding window analysis and trend prediction in step S4.

[0061] In step S305, during the initial filling stage, the flow front of the high-transmittance silicone material has not yet reached the location of each high-precision air pressure sensor, and the pressure inside the mold cavity shows a rapid downward trend. The readings of each high-precision air pressure sensor mainly reflect the pressure state of the residual gas inside the mold cavity.

[0062] When the high-transparency silicone material flow front reaches the location of each high-precision air pressure sensor in sequence, the reading of the corresponding high-precision air pressure sensor changes abruptly, reflecting the advancement process of the high-transparency silicone material filling front.

[0063] As filling continues, the gas inside the mold cavity is continuously discharged, and the pressure continues to decrease. The pressure difference between the high-precision air pressure sensor at the mold cavity inlet and the high-precision air pressure sensor at the corner changes over time, providing a data basis for the pressure gradient analysis in step S4.

[0064] Step S4: The controller filters and differentiates the online collected pressure data to calculate the pressure drop rate dP / dt. Then, it compares dP / dt with a preset threshold to identify the residual bubble state within the mold cavity. Based on the identification result, it retrieves the corresponding adjustment strategy from the control strategy table and automatically controls the vacuum pump group, exhaust valve group, and filling drive device to perform corresponding actions until the pressure within the mold cavity drops below 1 kPa and the pressure curve stabilizes. Figure 2 As shown, the adaptive exhaust control process includes the following sub-steps: In step S401, the controller receives digital pressure data from each monitoring point transmitted by the data acquisition module in real time, and the signal processing module first performs digital filtering and noise reduction on the raw pressure data.

[0065] Digital filtering employs a Kalman filter to preprocess the raw pressure data. The Kalman filter uses the time series of pressure data as observations and suppresses electromagnetic interference generated by high-voltage switchgear and frequency converters, as well as measurement noise caused by mold vibration, through prediction and iterative updates. The state-space model parameters of the Kalman filter are determined based on prior knowledge of cavity pressure changes during vacuum molding. The process noise covariance matrix and measurement noise covariance matrix are set based on the noise characteristics of the high-precision air pressure sensor and the mold vibration level.

[0066] After filtering, the signal processing module performs baseline correction on the filtered pressure data. Baseline correction is achieved by subtracting the offset measured by the high-precision pressure sensor under a known vacuum reference from the filtered pressure data, in order to eliminate the zero-point drift and temperature drift of the high-precision pressure sensor itself caused by temperature changes and long-term operation.

[0067] In step S402, the signal processing module performs a differential operation on the corrected pressure data to calculate the slope of the pressure-time curve, i.e., the pressure drop rate dP / dt.

[0068] The calculation method for dP / dt is as follows: within a sliding time window of length N, the pressure value corresponding to the beginning of the window is taken. Pressure value corresponding to the end of the window , and The units are all kPa. Calculation and The difference between the two times is then divided by the time difference Δt between the start and end times of the window, where Δt is in seconds. The formula is as follows:

[0069] The unit of dP / dt is kPa / s; the length N of the sliding time window is determined according to the dynamic characteristics of the system and the sampling frequency, with a typical value of 5 to 10 sampling periods, corresponding to 100ms to 200ms.

[0070] The above filtering and differential calculation steps transform the original pressure signal into the characteristic parameter dP / dt that reflects the exhaust dynamics, providing a quantifiable judgment index for subsequent residual gas identification.

[0071] In step S403, the controller compares the calculated dP / dt with a preset threshold, and the comparison logic covers three judgment scenarios.

[0072] Scenario 1 is the normal exhaust state. When dP / dt remains stable and the absolute value of dP / dt continues to decrease, it indicates that the air bubbles in the mold cavity are being discharged smoothly and the cavity pressure shows a normal exponential decay law. At this time, the adaptive control algorithm maintains the current motor speed of the vacuum pump group and the current valve opening of the exhaust valve group unchanged, and continues to operate at the current pumping rate and exhaust port cross-sectional area.

[0073] Scenario 2 is the residual bubble identification state. When a sudden change in dP / dt is detected, that is, when the absolute value of the pressure drop rate changes from steep to slow or a pressure plateau occurs, it is determined that there are residual unremoved bubbles in the mold cavity. The specific triggering conditions are divided into two modes.

[0074] Scenario 3 is an abnormal pressure fluctuation state. When dP / dt fluctuates irregularly and the fluctuation amplitude exceeds the preset amplitude threshold, it is determined that there is an abnormal disturbance in the mold cavity. The preset amplitude threshold is determined based on the statistical fluctuation range of dP / dt under normal venting conditions, and is taken as 3 times the standard deviation of normal fluctuation. Abnormal disturbance may be caused by the migration, rupture or regeneration of bubbles in the mold cavity.

[0075] The above-mentioned judgment logic enables the controller to identify the exhaust status and residual bubbles in the cavity online based on the characteristics of the pressure drop rate dP / dt.

[0076] To further differentiate between different types of residual air bubbles, the controller also simultaneously analyzes the pressure gradient between monitoring points; assuming the pressure measured by the high-precision air pressure sensor at the mold cavity inlet is... The high-precision barometric pressure sensor in the corner measured the pressure as follows: Calculate the pressure difference:

[0077] The unit of ΔP is kPa. When ΔP exceeds the preset gradient threshold, which is 0.5 kPa, it indicates that bubbles accumulate in local areas of the mold cavity, such as corners or where the flow channel cross-section changes. When ΔP is stable within a small range, i.e., when ΔP is less than the preset gradient threshold, it indicates that the bubbles are diffusely and uniformly distributed.

[0078] The pressure gradient information mentioned above is used for the selection of subsequent graded regulation strategies.

[0079] In step S404, when scenario two is triggered, the controller further distinguishes between the slope mutation mode and the pressure plateau mode.

[0080] The trigger condition for the slope mutation mode is that the absolute value of dP / dt decreases by a preset amount in a short period of time. The preset amount is more than 50%, that is, the percentage decrease of the absolute value of dP / dt in a short period of time exceeds 50%. The slope mutation indicates that the venting resistance in the mold cavity increases and the bubble venting speed slows down. There may be large-sized bubbles or multiple bubbles gathered in a specific area of ​​the mold cavity.

[0081] The trigger condition for the pressure plateau mode is that the pressure change is lower than the preset pressure change threshold and lasts for more than the preset plateau time. The preset pressure change threshold is 0.1 kPa and the preset plateau time is 0.5 s. The appearance of the pressure plateau indicates that the vacuum pump group continues to pump air but the pressure in the mold cavity no longer continues to decrease, indicating that there are closed bubbles that hinder the gas discharge.

[0082] Based on the pressure gradient ΔP calculated in step S403, the controller further refines the residual bubble state into three types: diffuse microbubble type, where the absolute value of dP / dt is consistently higher than the normal threshold, ΔP is less than 0.5 kPa, and the pressure curve has no obvious abrupt change or plateau period; local aggregation type, where the slope of dP / dt changes abruptly, and ΔP exceeds 0.5 kPa, indicating that the bubbles are aggregated in a local area; and closed island type, where a pressure plateau period occurs, and the ΔP distribution is stable but the overall pressure level remains high, indicating that the bubbles are sealed and encased by high-transmittance silicone material and isolated from the exhaust port.

[0083] The controller indexes the corresponding adjustment strategy in the control strategy table based on the refined bubble state type.

[0084] Step S405: The controller has a built-in control strategy table, which is pre-stored in the controller's non-volatile memory. The control strategy table records the mapping relationship between different pressure curve characteristics and corresponding control strategies. The control strategy table is constructed based on the following: During the production debugging phase, for each type of bubble state, the optimal vacuum pump speed adjustment, exhaust valve opening adjustment, and filling rate adjustment are determined through orthogonal experiments or single-factor experiments. The test results are written into the control strategy table, and the internal parameters can be adjusted according to actual needs during subsequent production.

[0085] For diffuse microbubble type, the controller performs the following adjustment operations: it sends a speed adjustment command to the frequency converter of the vacuum pump group, gradually increasing the speed of the vacuum pump motor by 10% to 15% from the current level to avoid microbubbles from bursting into smaller bubbles due to sudden pressure drop; at the same time, it sends an opening adjustment command to the exhaust valve group, increasing the cross-sectional area of ​​the exhaust port by 15% to 25% from the current level to reduce exhaust resistance and form a continuous and stable negative pressure gradient; it does not operate the filling drive device to maintain the normal filling rate and prevent filling fluctuations from introducing new disturbances.

[0086] For locally clustered bubbles, the controller automatically performs the following adjustments: it sends a pause command to the filling drive device, pausing the filling of the high-transparency silicone material for 1 to 2 seconds, providing a time window for the trapped bubbles to escape in a static state; at the same time, it starts a secondary vacuum replenishment program, allowing the vacuum pump unit to continue working for 3 to 5 seconds during the filling pause, further reducing the pressure inside the mold cavity to below 0.5 kPa; after the pause ends, the controller sends a slow start command to the filling drive device, allowing the filling rate to gradually return to the original set value within 1 second, preventing the bubbles from being trapped again due to the filling impact.

[0087] For the closed-island type, the controller performs tiered intervention. The first-level adjustment is the same as the localized cluster type, involving pausing filling and performing a second vacuum pumping operation. If the pressure plateau is relieved within 5 seconds after the second vacuum pumping, the process continues. If the pressure plateau is not relieved after the first-level adjustment, the second-level adjustment is initiated: the controller sends a rapid opening and closing command to the exhaust valve group, quickly closing the exhaust valve from its current opening and then reopening it to its original opening within 0.2 seconds, creating a momentary pressure disturbance. This causes a brief rise and fall in pressure within the mold cavity for about 0.1 seconds, impacting the interface of the closed air bubbles, causing them to rupture or change shape, thereby reconnecting them to the exhaust channel. The entire operation only changes the valve state, does not introduce any external media, and does not cause substantial damage to the vacuum environment. If the pressure plateau still exists after the second-level adjustment, the controller determines that there is a serious defect in the mold cavity, issues an alarm signal, and stops the current molding cycle, awaiting manual inspection.

[0088] In response to abnormal pressure fluctuations, the controller sends a speed reduction command to the filling drive device, reducing the filling rate by 15% to stabilize the flow of high-transmittance silicone material and reduce disturbance to the formed bubbles. At the same time, it sends an opening adjustment command to the exhaust valve assembly, increasing the exhaust valve opening by 10% to reduce exhaust resistance and improve bubble escape efficiency.

[0089] In step S406, after the controller completes the above adaptive adjustment operation, it re-enters the monitoring state and continuously collects and analyzes the pressure data. If it is determined that bubbles still exist, the corresponding adaptive adjustment operation is repeated until the pressure curve tends to stabilize and the pressure inside the mold cavity drops below the preset pressure threshold. The preset pressure threshold is 1 kPa. When the pressure inside the mold cavity drops below 1 kPa and the pressure curve remains stable within the set time window (set time window is 2 s), the controller determines that the bubbles have been discharged, step S4 ends, and the process proceeds to step S5.

[0090] It should be noted that during all the judgment and adjustment processes from steps S401 to S406, the controller independently analyzes and processes the pressure data of each monitoring point in the mold cavity, and comprehensively determines the overall exhaust state of the mold cavity based on the judgment results of each monitoring point; only when the pressure data of all monitoring points meet the stability conditions will the controller finally determine that the exhaust process is completed; the multi-point collaborative monitoring mechanism can avoid misjudgment caused by the failure of a single high-precision air pressure sensor or the abnormality of a local area.

[0091] Step S5: After confirming the exhaust is complete in step S4, stop filling and vacuuming, and maintain the temperature and vacuum pressure in the mold cavity at the set value, so that the high-transparency silicone material completes the cross-linking and curing reaction under static conditions to form a high-transparency silicone button solid elastomer product with precise dimensions and dense internal structure.

[0092] In step S501, the controller sends a stop filling command to the filling drive device, and the servo motor of the filling drive device stops running, the injection screw stops advancing, and no longer delivers high-transparency silicone material to the mold cavity.

[0093] At the same time, the controller sends a stop vacuuming command to the frequency converter of the vacuum pump group. The frequency converter stops outputting drive current to the vacuum pump motor, the vacuum pump motor stops running, and the exhaust valve group receives the closing command from the controller. The proportional solenoid valve switches to the closed position, sealing the exhaust channel of the mold cavity, and the vacuum state inside the mold cavity is maintained.

[0094] In step S502, during the pressure holding and curing stage, the mold temperature is maintained at the preheating temperature set in step S1, typically 180°C; the pressure inside the mold cavity is maintained at the vacuum state reached at the end of step S4, and the vacuum pump group is no longer actively pumping air out. The vacuum pressure inside the mold cavity is passively maintained by the sealing of the closed cavity.

[0095] The holding time is set to a preset holding time, which ranges from 50s to 80s. The specific value is determined based on the cross-linking and curing characteristics of the high-transparency silicone material. In one specific implementation, the holding time is set to 60s. The holding time is determined based on the positive vulcanization time of the high-transparency silicone material at 180℃. The positive vulcanization curve of the high-transparency silicone material is obtained by testing with a vulcanizing instrument. The positive vulcanization time is taken as the benchmark value of the holding time, and then adjusted according to the thickness of the product.

[0096] In step S503, during the pressure holding and curing process, the high-transparency silicone material undergoes a cross-linking and curing reaction under the high temperature and vacuum environment in the mold cavity; the cross-linking and curing reaction causes the linear silicone molecular chains in the high-transparency silicone material to form a three-dimensional network structure through the cross-linking agent, and the high-transparency silicone material gradually transforms from a liquid state into a solid elastomer.

[0097] During the pressure holding and curing process, maintaining the pressure inside the mold cavity ensures the dimensional accuracy and internal density of the high-transparency silicone keypad product, preventing shrinkage, deformation, or internal defects caused by pressure relaxation. The uniform and stable temperature of the mold ensures that the cross-linking reaction occurs simultaneously in all parts of the high-transparency silicone keypad product, avoiding differences in curing degree and residual internal stress caused by uneven temperature.

[0098] In step S504, during the pressure holding and curing stage, the controller continuously receives the actual mold temperature from the mold temperature sensor and the mold cavity pressure data from the high-precision air pressure sensor, and monitors the temperature and pressure parameters during the pressure holding and curing stage online.

[0099] The controller polls and collects the actual temperature data and pressure data inside the mold cavity according to the preset sampling period. It compares the actual temperature data and pressure data inside the mold cavity with the preset allowable deviation range. When the temperature deviation exceeds ±2℃ or the pressure rise inside the mold cavity exceeds the preset warning value, the controller issues a warning signal.

[0100] Once the pressure holding time reaches the preset value, the controller sends a curing completion signal, the pressure holding and curing stage ends, and the process is ready to enter the cooling stage.

[0101] The above steps, under static sealing conditions after venting, utilize a stable high temperature and vacuum environment to drive the high-transparency silicone material to complete cross-linking and curing, so that the high-transparency silicone keypad product is shaped under pressure, and the venting result of step S4 is cured into the internal quality of the high-transparency silicone keypad product.

[0102] Step S6: After the pressure holding and curing is completed, turn off the heating and start the cooling system to reduce the mold temperature to the preset safe demolding temperature. Then open the mold and take out the molded high-transparency silicone button from the mold cavity. After quality inspection, the entire molding cycle is completed.

[0103] In step S601, the controller sends a stop command to the heating and temperature control device, and the resistance electric heating plate is de-energized and stops heating; at the same time, the controller starts the cooling system to cool down the mold.

[0104] The cooling system can be either water-cooled or air-cooled. Water-cooled systems use pre-machined cooling channels inside the mold to circulate cooling water, which removes heat from the mold through convection heat transfer, resulting in higher cooling efficiency. Air-cooled systems use fans to force airflow onto the outer surface of the mold, which dissipates heat from the mold surface to the surrounding environment through air convection. While the cooling efficiency is relatively lower, the equipment cost is also relatively lower.

[0105] The above-mentioned cooling control allows the mold to cool down smoothly from the high temperature of vulcanization to the demolding temperature range, avoiding deformation or surface damage of the high-transparency silicone button products due to excessive temperature during mold opening. At the same time, the cooling method provides two options that can be selected according to the actual production line conditions and mold structure.

[0106] In step S602, during the cooling process, the controller continuously receives the actual temperature of the mold from the mold temperature sensor and monitors the trend of mold temperature change online. When the mold temperature drops below the preset cooling temperature, the controller determines that the cooling stage has ended. The preset cooling temperature is 80℃. The preset cooling temperature is determined based on the mechanical strength and thermal stability required for the high-transparency silicone button product during demolding. At 80℃, the high-transparency silicone button product has completed cross-linking and curing and has sufficient rigidity, which can maintain dimensional accuracy and appearance integrity during ejection and material removal.

[0107] In step S603, after the cooling stage is completed, the controller sends an opening command to the mold drive device. The mold drive device drives the upper mold to open upward along the guide post, so that the upper mold and the lower mold are separated and the mold cavity is exposed.

[0108] In step S604, after the upper mold is fully opened, the molded high-transparency silicone button is ejected from the mold cavity of the lower mold using an ejection mechanism. The ejection mechanism consists of an ejection plate and an ejector rod installed on the back of the lower mold. The ejector rod passes through the lower mold and extends to the bottom of the mold cavity. Alternatively, the high-transparency silicone button can be removed manually by the operator. The removed high-transparency silicone button then enters the quality inspection stage.

[0109] In step S605, the finished high-transmittance silicone button undergoes visual inspection, dimensional measurement, and light transmittance testing in sequence.

[0110] Visual inspection involves checking the surface of the finished product for defects such as air bubbles, missing materials, or uneven coloring under standard light sources. Dimensional measurement verifies whether the outline dimensions of the high-transmittance silicone keypad meet the design tolerance requirements. Light transmittance testing checks whether the optical transmittance and light transmission uniformity of the high-transmittance silicone keypad meet the product quality standards.

[0111] After passing inspection, the high-transparency silicone keypad products will proceed to the next process or be directly packaged and shipped.

[0112] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention. Therefore, the embodiments should be regarded as exemplary and non-limiting in all respects.

[0113] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment includes only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A bubble-free vacuum molding method for high-transmittance silicone keypads, characterized in that, Includes the following steps: During the process of filling the mold cavity with high-transmittance silicone material, high-precision air pressure sensors arranged in multiple different positions in the mold cavity are used to collect pressure data of each monitoring point in real time at a preset sampling frequency, and the pressure data is transmitted to the controller. The controller performs filtering and differentiation on the received pressure data, calculates the rate of change of pressure over time, compares the rate of change of pressure over time with a preset threshold, and identifies whether there are residual air bubbles in the mold cavity based on the comparison result. When residual bubbles are identified based on the rate of change of pressure over time, the controller automatically adjusts the rotation speed of the vacuum pump group connected to the mold cavity and / or the opening of the exhaust valve group according to a preset control strategy table, and selectively controls the start / stop of the filling drive device or the filling rate. When the pressure data meets the preset stability conditions and the pressure value drops below the venting completion threshold, venting and filling are stopped, pressure holding and curing are performed, and the finished product is removed after cooling.

2. The bubble-free vacuum molding method for high-transmittance silicone buttons according to claim 1, characterized in that, The high-precision air pressure sensor comprises at least four sensors, which are respectively arranged at the gate inlet of the mold cavity, the top center area of ​​the mold cavity, and the two opposite corners of the mold cavity away from the gate.

3. The bubble-free vacuum molding method for high-transmittance silicone buttons according to claim 1, characterized in that, Before the controller performs filtering and differentiation operations on the received pressure data, it also includes: The controller establishes an independent time-series pressure dataset for each monitoring point, and performs filtering, differentiation, and feature extraction on the pressure data of each monitoring point independently. The controller comprehensively determines the overall venting state of the mold cavity based on the comparison results of the pressure change rate over time at all monitoring points with a preset threshold. The venting process is determined to be complete only when the pressure data at all monitoring points meet the preset stability conditions.

4. The bubble-free vacuum molding method for high-transmittance silicone keypads according to claim 1, characterized in that, The controller compares the rate of change of pressure over time with a preset threshold to identify residual bubbles in the following ways: When the absolute value of the rate of change of pressure over time is detected to decrease by more than a preset percentage threshold within a preset time, it is determined to be a slope change mode, indicating the presence of locally aggregated bubbles. When the detected pressure change is lower than the preset pressure change threshold and the duration exceeds the preset plateau period time, it is determined to be a pressure plateau period mode, indicating the presence of closed island-type bubbles.

5. The bubble-free vacuum molding method for high-transmittance silicone buttons according to claim 4, characterized in that, Execute the corresponding adjustment strategy based on the different bubble types identified: When a locally aggregated bubble is identified, the controller sends a pause command to the filling drive device to pause the filling for a first preset time and starts a secondary vacuum replenishment procedure, so that the vacuum pump group continues to work for a second preset time during the filling pause. When a closed, isolated bubble is identified, the controller first executes the pause filling and secondary vacuum replenishment procedure. If the pressure plateau is not relieved within a preset judgment time after the secondary vacuum replenishment is completed, a rapid opening and closing command is further issued to the exhaust valve group to quickly close the exhaust valve and then reopen it to the original opening degree within a preset very short time, creating an instantaneous pressure disturbance.

6. The bubble-free vacuum molding method for high-transmittance silicone buttons according to claim 4, characterized in that, The controller also simultaneously analyzes the pressure gradient between each monitoring point: The pressure difference between the pressure measured by a high-precision air pressure sensor at the gate inlet of the mold cavity and the pressure measured by high-precision air pressure sensors at two opposite corners of the mold cavity away from the gate is calculated. When the pressure difference exceeds a preset gradient threshold, it is determined that bubbles have accumulated in a local area of ​​the mold cavity; when the pressure difference is less than the preset gradient threshold, it is determined that the bubbles are diffusely and uniformly distributed. The controller assists in selecting the corresponding adjustment strategy based on the determination result of the pressure difference.

7. The bubble-free vacuum molding method for high-transmittance silicone buttons according to claim 1, characterized in that, The method further includes a mold preheating step before the filling step: The controller divides the mold preheating process into a rapid heating stage, a heat preservation and stabilization stage, and a stable holding stage; in the rapid heating stage, heating is performed at a preset maximum power. When the mold temperature approaches the target temperature, it enters the heat preservation and stabilization stage, where the heating power is reduced by a PID control algorithm to suppress temperature overshoot; when the mold temperature reaches the target temperature, it enters the stabilization and holding stage, where the temperature fluctuation is controlled within a preset range by dynamically fine-tuning the heating power.

8. The bubble-free vacuum molding method for high-transmittance silicone buttons according to claim 1, characterized in that, The preset stability condition is: Within a preset time window, the controller performs sliding window analysis on the pressure data of each monitoring point. The pressure curves of each monitoring point tend to be stable and the rate of change of pressure over time tends to be zero. At the same time, the pressure in the mold cavity drops below the exhaust completion threshold.

9. The bubble-free vacuum molding method for high-transmittance silicone buttons according to claim 1, characterized in that, The method further includes a material preparation step before the filling step: A refractive index matching light-transmitting filler is added to the high-transmittance silicone material, and the refractive index of the refractive index matching light-transmitting filler is controlled to deviate from the refractive index of the silicone matrix within a preset matching range.

10. The bubble-free vacuum molding method for high-transmittance silicone buttons according to claim 1, characterized in that, After the pressure holding and curing process is completed, a cooling and demolding step is also included: Turn off the heating and start the cooling system to lower the mold temperature to the preset safe demolding temperature. Then open the mold and remove the molded high-transparency silicone button from the mold cavity.

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